Studies have been designed to investigate the effects of narcotic analgesics on brain amine levels and neuroendocrine function. The levels or turnover of brain amines (norepinephrine, dopamine, serotonin, acetylcholine) will be correlated with some parameters of anterior pituitary activity (adrenocorticotropin, thyrotropin, growth hormone and luteinizing hormone). Localization of the central sites and pathways of these agents will be determined by the injection of microquantities of the drugs into specific brain sites, while using a neuroendocrine response for an endpoint, and by measuring morphine distribution in brain by radioimmunoassay and immunohistofluorescence.